This invention relates to an antistatic agent for polymers.
Most organic polymers are poor conductors of electricity. As such, they cannot be satisfactorily used without modification in applications which require a conductive or semi-conductive material, such as static dissipation materials.
Due to their beneficial properties such as low cost, easy processability, good strength and light weight, it is often desirable to substitute polymeric materials into applications which in the past required metals or other materials. Accordingly, it has been attempted to prepare semi-conductive or conductive polymers.
It is known, for example, to incorporate conductive fibers, particulates or powders into a polymer in order to increase its conductivity. Although good conductivity can be achieved in this manner, the high loadings of filler material (generally 20% or more) needed to obtain such conductivity greatly alter properties of the polymer, often making it unsuitable for its desired purpose. In addition, such highly filled polymers are often much more expensive than the unfilled polymer. Yet another problem encountered with certain such fillers, especially fibers, is they often break, oxidize or otherwise lose their effectiveness over time.
It is also known to treat the surfaces of polymers with amines or quaternary ammonium compounds to render them antistatic. However, such treatments are often removed from the polymer during its normal use, causing the polymer to lose its antistatic properties.
Another approach has been to incorporate ionic salts into a polymer to increase its conductivity. For example, in Dupon et al. J. Elec. Chem. Soc. 128:715 (1981) it is taught to incorporate salts such as sodium thiocyanate into high molecular weight poly(ethylene oxide) to increase its conductivity. French Pat. Nos. 2,442,513-4 demonstrate the dissolution of mixed alkaki metal thiocyanate salts into poly(alkylene oxide) polymers for the same reason. In these references, the concentration of salt is generally at least about 5 weight percent, and is preferably as high as about 25 weight percent. Such a high level of salt often imparts undesirable properties to the polymer, such as sensitivity to water. When such levels of salts are employed in a flexible polyurethane foam, the foam often fails, prunes or collapses due to the formation of undesired closed cells.
Although inclusion of these salts has improved the conductivity of the polymers, it would be desirable from the standpoint of utility and cost to further increase the conductivity of the polymer while minimizing the salt content.